Anti-slip relay for hoist control



Aug. 1, 1967 o. JENSEN 3,334,287

ANTI-SLIP RELAY FOR HOIST CONTROL Filed July 5, 1963 p by the controller,

United States Patent O FOR HOIST CONTROL Pa., assignor to I-T-E Circuit Philadelphia, Pa., a corporation of 3, ANTI-SLIP RELAY Otto Jensen, Malvern, Breaker Company, Pennsylvania Filed July 5, 1963, Ser. No. 292,964 3 Claims. (Cl. S18-369) This invention relates to electrical hoists, and more specifically relates to a novel relay arrangement for electrical hoists which automatically applies a hoist brake and de-energizes the hoist motor when hoist rotation occurs in a direction'opposite to that commanded by the controller.

In the operation of electrical hoists, Isuch as the hoist shown in copending application Ser. No. 212,335, tiled July 25, 1 962 entitled, Hoist Control System, in the name of Donald I. Bohn and assigned to the assignee of the present invention, now U.S. Patent No. 3,166,701 and during hoisting operation it is possible that the operator has move-d the controller to a position which provides insuiicient power to overcome the torque of the load whereby, when the hoist brake is released, the load will unexpectedly move in a direction opposite to that desired.

The principle of the present invention is to automa-tically measure 4or monitor the direction of rotation of the rotor of a hoist and at the instant it is 'determined that the rotor rotates in a wrong direction, a brake is automatically applied to the hoist and the hoist motor de-energized until the operator moves the controller to a suiciently high point at which the hoisting torque exceeds the load.

In a particular embodiment of the invention, the rotor of the hoist .is provided with a tachogenerator having a field coil thereon. The eld coil is then energized in a direction depending upon whether hoisting or lowering operation is commanded by the controller, and the output of the armature winding is then connected in series with a relay and a diode. The polarity of vthe-se connections is such that if the tachogenerator output appears in the conduction direction of the diode, this indicates that the rotor is rotating in an opposite direction to that commanded whereby a relay coil may be actuated by the forward conduction current of the diode to ultimately apply appropriate brake means and to de-energize the motor. Thereafter, the relay is reset by turning the controllerto an oli position followed by a readjustment of the controller to a suiciently high point to permit rotation of the rotor in the required direction. If, however, motor rotation is in the proper direction, the output of the tachogenerator is .in the blocking direction of the diode so that the relay is not energized.

Accordingly, a primary object of this invention is to prevent the unexpected movement of the load of a hoist in the wrong direction.

Another object of this invention is to automatically apply a brake to a hoist when the hoist load moves downwardly while the hoist controller requires upwardlmovement of the load.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 schematically illustrates a hoist motor having the novel control structure of the present invention.

FIGURE 2 is a controller chart for the hoist of FIG- URE 1.

FIGURE 3 illustrates the hoist torque characteristics of the hoist of FIGURES l and 2.

As is best shown in FIGURE 3 which illustrates a typical constant horsepower electrical hoist system speedtorque characteristic, it will be seen that for each hoist point position '1 through 5 of the hoist controller, the hoisting speed varies inversely with the load being lifted. That is to say, the operator lof the hoist will be provided with a control panel having tive switch positions 1 through 5 for hoisting operation. Each of the switch positions corresponds to ya different combination of required hoist speeds and torque.

Assume, for example, that a load L is to be lifted. From FIGURE `3 it can be seen that the controller must be brought to point 3 or to some higher point 4 or 5 since, if the controller is at one of the lower positions 1 or 2, the torque -developed by the motor will be insuicient for hoisting. Therefore, to start hoisting, the operator moves the controller to successively higher hoist points until he reaches a point where the hoisting torque exceeds the load. If for example, the operator moves the controller to point 3, the load will be lifted at a speed S-. If now the operator wants to continue hoisting at a lower speed, he will move the controller handle back to the lower point 2. However, the torque `developed at this lower point is insuliicient to continue hoisting, so that the load will now move down, even though the controller is in a hoist point. This action is unexpected Iby the controller and, of course, is highly undesirable.

The principle of the present invention relates to a novelirelay which may be called an anti-slip relay, which operates to apply the hoist brake and disconnect the motor as soon as the direction of motion of the hoist changes to lower the load while the controller is in a hoist position. More specifically, the invention includes a means for detecting this change in motion when the direction of motor rotation is opposite to that required by the controller position, and means for stopping the drive when this `condition is detected.

' One embodiment of the invention is shown in FIGURE 1 for a motor 20 having a stator 21 and rotor 22. The -hoist system may be of the .type set forth in above noted copending applicaion Ser. No. 212,35 5 wherein A-C power is connected to terminals 23, 24 and 25 through the three-phase contact 26. The rotor 22 of the hoist system is then provided with a suitable -brake means 27 which can, for example, be of the type shown in copending `application Ser. No. 246,723 in the name of G. E. Heberlein, tiled Dec. 24, 1962 entitled Load Responsive Brake Release and assigned to the assignee of the present nvention now U.S. Patent 3,158,233, and is released only when the brake release coil 28 is energized.

The rotor 22 is also connected to a tachogenerator 29 which has a field winding 30. The main source of control power for the control system may be a suitable D-C source which'is connected to terminals 31 `and 32 wherein a plurality of parallel circuits are connected across terminals 31 and 32. Thus, an undervoltage relay coil 33 having .contacts 33a and 33h form a first circuit; ahoist coil 34 having hoist contacts 34a and 34b and a lower relay coil 35 having lower contacts 35a and 35b, are provided. These three circuits additionally include contacts 36, 37 and 33 which are operated from the master control switch or controller, and are opened and closed as indicated in the diagram of FIGURE 2. That is to say, contact 36 will be closed when the master control switch is off. Contact 37 will be closed when the master control switch is on any of its hoist points 1 through 5. Contact 38 will be closed when the master control switch is on any of its lower control -points 1 through 5.

A further circuit including contactor coil 39 is -provided wherein contactor 39 is adapted to operate contactors 26 of stator 21. More specifically, so long as coil 39 is energized, contactors 26 will be closed, while the contactors 26 are opened when coil 39 is de-energized.

In accordance with the invention, the output of tacho-l generator 29 is connected in `series with relay coil 40 and a diode 41a. The relay coil 40 is then associated with a normally closed contact 41 in series with undervoltage relay 33.

D-C voltage from terminals 42 and 43 is then applied at points between contacts 34a and 35b and contacts 35a `and 34h respectively. The voltage applied to terminals 42 and 43 may be derived from the control power source of terminals 31 and 32.

The operation of the circuit of FIGURE l is as follows:

Assuming first that the master control switch is on a hoist position sufliciently high to cause hoisting operation, the contact 37 will be closed so that coil 34 is energized. Therefore, contacts 34a and 34b are closed whereby D-C voltage at terminals 42 and 43 is applied across the brake release coil 28 to move brake 27 to its release position and permit rotation of rotor 22. This D-C voltage is also applied to field winding 30. Since tachogenerator 39 is rotating in the proper direction, it will have a voltage output as indicated by the polarity markings so that current ow through relay coil 40 is blocked by the diode 41a. Therefore, contact 41 remains closed so that relay coil 33 is energized and contacts 33a and 33b are closed. Since contact 33b is closed, control power is applied to coil 39 so that contactor 26 remains closed.

Assume now that the operator wishes to decrease the hoist speed and moves back to a lower hoist point. If this lower hoist point, .as shown in FIGURE 3, is insuicient to provide positive torque to the hoist and the load now begins to drop, the tachogenerator 29 reverses its polarity. A forward current now passes through diode 41a to energize relay coil 40. This causes contact 41 to open so that undervoltage relay 33 is de-energized and contacts 33a and 33b move to their normally open position. The opening of contact 33b causes the de-energization of coil 39 whereby contact 26 is immediately opened to de-energize stator 21. At the same time, relay 34 is de-energized so that contacts 34a and 34b open to de-energize the brake release coil 21, whereby brake 27 is immediately applied to the rotor 22.

' Note that this sequence occurs automatically so that no directive operation is required by the operator.

In order to resume opeartion, the operator must now move his master control switch to the off position so that contact 36 is closed to permit re-energization of undervoltage coil 33 and reclosing of contacts 33a and 33b. This then closes contactor 39 so that power is -applied to stator 21. Thereafter, a sufficiently high hoist point is set on the master control switch so that contact 37 is closed to energize hoist relay coil 34, whereby the brake release coil 28 is released and hoisting operation is resumed.

It is to be specifically noted that the brake release structure may be formed in the manner shown in -copending application Ser. No. 246,723, in the name of Heberlein, tiled Dec. 24, 1962', entitled Load Responsive Brake Release, now U.S. Patent 3,158,233, and assignedto the assignee of the present invention, which will prevent resaid rotor rotates in a lower direction; said stator sumption of hoisting until suicient torque is developed for lifting the load.

During the lowering mode of operation, it will be seen that contact 38 is closed to energize coil 35 so that contacts 35a and 35b are closed. This, again, permits release -of coil 28 and energizes field winding 30 with a polarity opposite to the polarity it assumes during hoisting operation. Therefore, the tachogenerator output during lowering will have a polarity which is appropriate to attempt to pass blocking current through diode 41a so long as the rotor lowers the load. If the load now suddenly changes during the lowering mode, the same protective operation will proceed to de-energize stat-or 21 and close the brake 27.

Although this invention has been described with respect to its preferred embodiments, it will now be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred therefore that the scope of this invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A hoist control circuit for an electrical hoist including a hoist motor having a stator winding, =a .rotor having a cooperating electrically energizable brake movable between a braking and released position, a master control switch for selectively energizing said stator winding from a voltage source to cause said rotor to rotate in a hoist or lower direction; and a rotation direction sensing mean-s connected to said rotor and said control switch; said rotation direction sensing means being operatively connected to said brake for applying said brake when said master control switch energizes said stator winding for rotation of said rotor in a hoi-st direction and winding being energized through contactor means; said rotation direction sensing means being operatively connected to said contactor means to open said contactor means when said master control switch energizes said stator winding for rotation of said rotor in a hoist direction said rotation direction sensing means including a tachogenerator and said rotor rotates in a lower direction; said tachogenerator having a field winding thereon; said lield winding being operatively connected to said master controller and being energized with a plurality dependent upon the operation of said hoist in a hoist or lower direction; said tachogenerator having an armature winding connected in series with relay means and a diode; said armature winding having an output current in the blocking direction of said diode when said rotor operates in a hoist direction when hoist operation is selected by said master control switch whereby said relay means is deenergzed; said relay means being operatively connected to said contactor means and said brake means to apply said brake and open said contactor when said relay means is energized.

2. A hoist control circuit for an electrical hoist including a hoist motor having a stator winding, a rotor having a cooperating electrically energizable brake movable between a braking and released position, a brake release core connected -to said brake operable responsive to an electrical output signal, la master control switch having a hoist direction position and a lower direction position for selectively energizing said stator winding from a voltage source to cause said rotor to rotate in a hoist or lower direction; and a rotation direction sensing means connected to said rotor and said control switch and generating an electrical output signal responsive to rotation of said rotor in a` lower direction when said control switch is in a hoist direction position; and rotation direction sensing means connected to said brake release core for moving said brake to said braking position when said master control switch energizes said stator winding for rotation of said rotor in a hoist direction and said rotor rotates in a lower direction; said stator winding being energized through contactor means; said rotation direction sensing means being operatively connected to said contactor means to open said -contactor means when said master control switch energizes said stator winding for rotation of said rotor in a hoist direction and said rotor rotates in a lower direction.

3. The control circuit as set forth in claim 2 wherein said direction rotation sensing means includes a tachogenerator.

References Cited UNITED STATES PATENTS Rathburn S18-369 X Vogt 318-382 X Berman S18-372 X Sanborn S18-369 X Zollinger 318--382 X ORIS L. RADER, Primary Examiner. l0 J. C. BERENZWEIG, I. I. BAKER, Assistant Examiners. 

1. A HOIST CONTROL CIRCUIT FOR AN ELECTRICAL HOIST INCLUDING A HOIST MOTOR HAVING A STATOR WINDING, A ROTOR HAVING A COOPERATING ELECTRICALLY ENERGIZABLE BRAKE MOVABLE BETWEEN A BRAKING AND RELEASED POSITION, A MASTER CONTROL SWITCH FOR SELECTIVELY ENERGIZING SAID STATOR WINDING FROM A VOLTAGE SOURCE TO CAUSE SAID ROTOR TO ROTATE IN A HOIST OR LOWER DIRECTION; AND A ROTATION DIRECTION SENSING MEANS CONNECTED TO SAID ROTOR AND SAID CONTROL SWITCH; SAID ROTATION DIRECTION SENSING MEANS BEING OPERATIVELY CONNECTED TO SAID BRAKE FOR APPLYING SAID BRAKE WHEN SAID MASTER CONTROL SWITCH ENERGIZES SAID STATOR WINDING FOR ROTATION OF SAID ROTOR IN A HOIST DIRECTION AND SAID ROTOR ROTATES IN A LOWER DIRECTION; SAID STATOR WIND ING BEING ENERGIZED THROUGH CONTACTOR MEANS; SAID ROTATION DIRECTION SENSING MEANS BEING OPERATIVELY CONNECTED TO SAID CONTACTOR MEANS TO OPEN SAID CONTACTOR MEANS WHEN SAID MASTER CONTROL SWITCH ENERGIZES SAID STATOR WINDING FOR ROTATION OF SAID ROTOR IN A HOIST DIRECTION SAID ROTATION DIRECTION SENSING MEANS INCLUDING A TACHOGENERATOR AND SAID ROTOR ROTATES IN A LOWER DIRECTION; SAID TACHOGENERATOR HAVING A FIELD WINDING THEREON; SAID FIELD WINDING BEING OPERATIVELY CONNECTED TO SAID MASTER 